The proposed research deals with the following aspects of sarcoplasmic reticulum structure and function. 1) The biosynthesis of sarcoplasmic reticulum (SR). The regulation of the biosynthesis on the Ca2 ion transport ATPase of SR will be analyzed in cell free systems, muscle cell cultures, and in whole animals. The role of intracellular free Ca2 ion in the regulation of gene-expression will be tested at the transcriptional and translational level. 2) Methods will be developed for the measurement of cytoplasmic free Ca2 ion concentration in cultured skeletal muscle using Ca sensitive microelectrodes and/or aequorin as probes. Changes in (Ca)2 ion will be correlated with expression of muscle proteins during development. 3) The mechanism of Ca2 ion transport will be studied with respect to the mode of involvement of phospholipids, and the role of Mg2 ion and K ion as counterions using rapid kinetic techniques.